100% FAKE
No doubt in my mind that the pictures are of a doctored 737-800.
The air con riser on the 737-300 is just fwd of the wing leading edge.
It is between the "H" & "E" of Helios and on picture 4 it is in front of the "H".
You will also see the over wing hatch is one window fwd of the over wing emergency light, on the doctored picture it is a few windows fwd of the light.
The last fact which has been pointed out, is that the APU exhaust is of an NG 737 type exhaust.